This invention relates to a device for eliminating Absolute Polarity inversion in a high-fidelity sound reproduction system. More particularly, this invention relates to a device usable with existing stereophonic sound reproduction systems for eliminating Absolute Polarity inversion therein.
Music and sound consist of pressure waves having "peaks" and "valleys." Should one desire to make a sound recording, the following conditions should exist:
(A) A "peak" should cause a positive movement in a microphone diaphragm at the time of the original recording and will result in a positive or forward movement in both loudspeakers upon playback. PA1 (B) If the opposite result occurs and the "peak" in the original live sound causes a negative or rearward motion in both loudspeakers during playback, the output of the sound reproduction system can be said to be in inverted Absolute Polarity.
The causes of Absolute Polarity inversion can be that the Absolute Polarity of the recording itself is inverted or that a component in the sound reproduction system is producing an Absolute Polarity inverted signal.
Absolute Polarity should not be confused with Relative Polarity. Incorrect Relative Polarity exists when a positive movement in the diaphragm of a recording microphone results, during playback of the recorded sound, in a positive movement in one loudspeaker and a negative movement in another loudspeaker. Correct Relative Polarity exists when a positive movement in the microphone diaphragm results, during playback, in both loudspeakers moving in the same direction (without regard as to whether this movement is positive or negative, thence in correct or inverted Absolute Polarity).
Well known techniques for compensating for Absolute Polarity inversion include the reversal of wires at the input terminals of speakers or at the output terminals of amplifiers. Alternatively, leads at the output terminals of an audio signal extraction component such as a phonograph cartridge may be reversed. A disadvantage of such a technique arises from the inconvenient location of the terminals of such components or the complexity of reversing certain leads such as cartridge leads. The terminals are frequently in places which are difficult to reach. Such a correction for Absolute Polarity inversion may thus require a major effort at rewiring. This effort is all the more burdensome if several successive played sound recordings each necessitate rewiring to adjust for the respective Absolute Polarities of the recordings.
Another technique for compensating for Absolute Polarity inversion involves the incorporation of an Absolute Polarity inverting switch in the sound reproduction system, for example, upstream of a preamplifier and downstream of a stereophonic cartridge. Such a method, however, is undesirable because it introduces additional distortion and signal degradation into the system.